Armature twitches out of position for single frame during animation render
I can't speak for vers's 2.8+ but this is a common occurance and the solution has often turned out to be as simple as saving the Blend file, exiting Blender, deleting any cache folder(s) found in both the project folder and Blender's 'Temporary' folder (as designated in pref's), then reloading the project again. Hope this helps in your case... It may also be that the armature is working against some other modifier or constraint